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VALORISATION DES AMAS DE SERPENTINITE PAR NANOTECHNOLOGIE. PARTIE I - OBTENTION DE LA SILICE POREUSE


SÂRBU ANDREI 1 *, MARA LUMINIĆąA 2, STOICIU FLORENTIN 2, BADILITA VIOREL 2, FRUTH VICTOR 3, IOVU HORIA 4, GAREA SORINA 4, MOTOC ĆžTEFANIA 5, SÂRBU LILIANA 1, BEDA MARIANA 1
(1)INSTITUT NATIONAL DE RECHERCHE - DÉVELOPPEMENT POUR CHIMIE ET PÉTROCHIMIE- ICECHIM BUCAREST, DÉPARTEMENT DES POLYMÈRES, SPL. INDEPENDENTEI NR. 202, SECTOR 6 BUCAREST, ROUMANIE (2)INSTITUT NATIONAL DE RECHERCHE - DÉVELOPPEMENT POUR MÉTAUX NON FERREUX ET

Issue:

SCSCC6, Volume VII, No. 2

Section:

Volume VII - No. 2 (2006)

Abstract:

After the old mining of asbestos, in the “Portile de Fier” Romanian natural reservation, by the Danube, at the Dubova mine, several dumps remained, containing mostly serpentinite (magnesium silicate). The dump serpentinite is a green-yellow soft rock, having Mohr hardness about 3, which has few utilisations. The tentative for solving the ecological aspects in the natural reservation impose imperiously the extinguishment of these dumps. It is why it is urgent to find new utilisation to this mineral. The work presents, firstly, a mineralogical analyse of the Dubova dumps. The mineralogical analyse proved that, in the samples taken from the dumps, all important members of the serpentine group are presents: antigorite and lizardite (lamellar forms), chrysotile (fibrous form) and olivine, which is the origin rock of the serpentine. The thermal diagrams of the serpenitinite revealed two strong endothermal effects in the 400 - 700 oC range, which are though to prove the two steps antigorite dehydration. The mineralogical analyse attested the possibility of utilisation of the serpentinite for the inorganic porous structures generation, because it has a homogenous composition referring to the major mineral phases (over 75%). These major phases are lamellar forms of antigorite and lizardite. Later, the work presents the studies for the porous silica preparation, performed by the attack with inorganic acids, namely: sulphuric, chlorhydric and nitric acids. A stoichiometric ratio between reactants was used. The reaction temperature was maintained at 96 oC and the reaction medium was stirred during the reaction time, at a constant stirring speed (500 rot/min). The reaction time for all reactions was the same: 2 hours. It is also discussed the influence of the kind of acid on the chemical composition of the two obtained phases: liquid phase and gel phase. The preliminary tests concerning the generation of the silica inorganic porous structures showed that the silica obtained by the acid attack, is contaminated with iron, aluminium, chrome and nickel, which are outgoing from the initial serpentine. After the two steps washing in boiling water and the drying 3 hours at 60 - 80 oC, the silica contains a lot of free water (which is probably retained in the pores), which was assessed by the losses at calcination (900 oC). Drying the gel, a porous silica was obtained, having a specific surface (assessed by BET) of 200-270 m2/g.

Keywords:

serpentinite, porous, silica, acid attack, silicon nitride.

Code [ID]:

CSCC6200607V02S01A0006 [0001092]

DOI:

Full paper:

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